Optical fibers and optical fiber bundles are often used for endoscopy and related (minimally invasive) medical methods because they offer good transparency together with flexibility. The ability to perform the operation, monitoring and chemical analysis of tissues with minimal disruption of the skin or internal organs of the patient is very promising in the medical field. Traditionally, silica optical fibers are used. Although silicon oxide is a biocompatible material, its use involves a serious health risk due to its fragility and the fact that potential fiber fragments can freely move inside the body and they are not detectable by conventional methods such as X-ray imaging. A possible solution to this issue can be the development of optical fibers based on biodegradable materials. Important benefit of bioresorbable fibers is that they do not need to be explanted after their use. We report on the optical power transmission tests of recently developed bioresorbable optical fibers based on phosphate glasses. Continuous-wave fiber lasers at 1080 and 1060 nm with output powers up to 7 W and a picosecond laser source at 515 nm with MW pulse peak power were used.
Hi-tech industrial or biotechnological laser applications request for picosecond pulsed 2-μm laser generating sub-1-J pulses in >kHz repetition range. At HiLASE center the development of the laser system with target to generate 1-J picosecond pulses with 1-kHz repetition rate has started. In this paper, we present a concept of the laser system and demonstrate recent results from the first part of the laser – the holmium fiber oscillator. The holmium fiber front-end is pumped by a continuous wave <1-W thulium fiber laser generating at wavelength of 1950-nm. Mode-locking operation in the oscillator is reached by dispersion management in the laser cavity. In this self-starting configuration we reached 45-mW of average power with repetition rate of 22.5-MHz with pulse energy of 2-nJ.
Hi-tech industrial or biotechnological laser applications request for picosecond pulsed 2-um laser generating sub-1-J pulses in >kHz repetition range. At Hilase development of laser system with target to generate 1-J picosecond pulses with 1-kHz repetition rate has started.
Design of the system based on Ho:YAG thin-disk generating at 2.1-um is divided into several phases. First phase includes demonstration of new mode-locked graphen-based saturable absorber Ho-doped fiber laser concept followed by preamplifier systems delivering 10-uJ pulses. Pulses are then amplified to >10-mJ level in Ho:YAG thin-disk regenerative amplifier operating at 10-kHz, and finally amplified in double stage cryogenically-cooled multi-pass amplifier to 1-J at 1-kHz so average output power reaches 1-kW in mid-IR.
We present a concept of this laser system with emphasize on the front-end and the first regen. The holmium fiber front-end is pumped by a continuous wave 0.5-W thulium fiber laser generating at wavelength of 1950-nm. Mode-locking in the oscillator is reached by graphene multilayer optical element as a passive saturable absorber (GSA). The GSA provides broadband wavelength operation and is promising for MIR sources. In the laser setup, the GSA is placed in a free-space cavity as a part of ring laser configuration. This oscillator produces <10-ps-pulses with ~nJ energy and <40-MHz repetition rate. The repetition rate reduces acousto-optic modulator, pulses are pre-amplified in a chain containing Ho-doped fibers and a single crystal fiber to 10-uJ/10-to-100-kHz, and seeded to thin-disk regen.
We expect demonstration of the front-end, detailed design of first regenerative amplifier and conceptual design of full system.